1. Field of the Invention
The subject invention resides in methods and apparatus for centering advancing tapes and has utility in tape transports employed in magnetic tape recording equipment and in other applications where a tape or tape-like web is to be centered onto a desired tape or web advance path.
2. Description of the Prior Art
The most frequently employed method for centering an advancing tape onto a desired path resides in the provision of members defining one or two guide edges. In practice, this has imposed considerable wear and tear on the tape and has rendered the system sensitive to tape width tolerances and snakiness. In the case of information recording tape, the mentioned prior-art solution has also introduced scrape flutter into the information signal.
It had, therefore, been proposed that fluid bearings be employed for centering purposes. In this connection reference is made to the U.S. Pat. Nos. 2,848,820, 2,908,495, 2,954,911, 2,967,674, 3,032,246, 3,087,664, and 3,281,040.
In reviewing the proposals contained in these patents, it will be noted that some of them provide only a single fluid bearing at each guide, which impairs an efficient centering action. Some prior art has attempted to counter this by generating trough-like air jets. This, however, bent the tape edges away from the bearing and maintained the tape edges bent during the operation of the equipment, thereby disturbing a desired generally flat tape configuration.
Another proposal developed a transverse pressure gradient in a single fluid bearing chamber. This required the tape edge to slide along a guide surface, which made tape centering sensitive to the snakiness of commercial grade tapes. Another proposal, which also employed only a single bearing chamber, required the provision of upright fixed flanges which rendered the bearing sensitive to tape width tolerances and snakiness and which tended to introduce scrape flutter in response to tape contact of either of the flanges.
The above mentioned deficiencies of prior-art proposals and systems also resulted in a loss of data in the tape margin which was engaged by a guide surface.